Shu Xin, Li Yan, Li Feng, Feng Jing-Yi, Shen Jia-Yu, Shi Zhou
Institute of Land Science and Property, School of Public Affairs, Zhejiang University, Hangzhou 310058, China.
Department of Environmental Engineering, College of Materials and Environmental Engineering, Hangzhou Dianzi University, Hangzhou 310018, China.
Huan Jing Ke Xue. 2019 May 8;40(5):2471-2482. doi: 10.13227/j.hjkx.201809052.
Land use cover change (LUCC) is one of the most important human activities that drive the evolution of the environment. It has great effect on the accumulation, distribution, and migration of heavy metals in the environment. Vegetation can absorb heavy metals directly, and it can also change the physical, chemical, and biological properties of soil and then control the mobility and activity of heavy metals in soil, which will eventually cause pollution of heavy metals in soil. In addition, the migration of heavy metals in soil is also affected by changes of landscape element composition and landscape pattern at sample points, plots, watersheds, and regional scales. Based on the soil sampling data and land use data of Ningbo city in 2003 and 2013, the decision tree classification method based on classification and regression tree algorithm was used to classify the land use and cover type. Single-factor pollution index and Nemero composite pollution index were used to evaluate the soil heavy metal pollution status. The landscape pattern indexes were used to explore the change of landscape patterns under different degrees of heavy metal accumulation. Finally, redundancy analysis and partial redundancy analysis were used to identify those landscape pattern factors that had the most significant impacts on the soil heavy metal accumulation in the study area. The results showed that:①The eight soil heavy metal elements including As, Cd, Cr, Cu, Hg, Ni, Pb, and Zn presented different degree of accumulation from 2003 to 2013 in the study area, of which Hg, Ni, and Cr had the highest degree of accumulation. Most of the study area has been polluted by heavy metals, and the pollution degree in the heavily polluted areas is still increasing. ②Higher accumulation degrees of heavy metals was not distributed entirely in areas where land use types have always been construction land, or in areas where other types of land use had been converted to construction land. A considerable proportion of heavy metals accumulated in areas where land use types have always been cultivated land or converted from other types to cultivated land. ③Heavy metal polluted areas have fragmented, complex, and aggregated landscape pattern, and the correlation between this kind of landscape pattern characteristics and soil heavy metal accumulation in arable land, residential land, and industrial land was the highest. ④The higher the aggregation degree of construction land patch, the higher the accumulation degree of most heavy metals. The accumulation degree of Cu, Hg, Pb, and Cd increased significantly with the increase of landscape diversity and shape complexity of agricultural land. The closer the distance to the mining site, the more obvious the effect on the increase of Cd content.
土地利用覆盖变化（LUCC）是推动环境演变的最重要人类活动之一。它对环境中重金属的积累、分布和迁移有很大影响。植被可以直接吸收重金属，还能改变土壤的物理、化学和生物学性质，进而控制土壤中重金属的迁移性和活性，最终导致土壤重金属污染。此外，土壤中重金属的迁移还受采样点、样地、流域和区域尺度上景观要素组成和景观格局变化的影响。基于2003年和2013年宁波市的土壤采样数据和土地利用数据，采用基于分类回归树算法的决策树分类方法对土地利用和覆盖类型进行分类。利用单因子污染指数和内梅罗综合污染指数评价土壤重金属污染状况。运用景观格局指数探究不同程度重金属积累下的景观格局变化。最后，通过冗余分析和偏冗余分析确定对研究区域土壤重金属积累影响最显著的景观格局因子。结果表明：①研究区域内，2003年至2013年期间，砷、镉、铬、铜、汞、镍、铅和锌这八种土壤重金属元素呈现出不同程度的积累，其中汞、镍和铬的积累程度最高。研究区域大部分已受到重金属污染，重度污染区域的污染程度仍在增加。②较高的重金属积累程度并非完全分布在一直为建设用地的区域，或其他土地利用类型已转变为建设用地的区域。相当一部分重金属积累在一直为耕地或从其他类型转变为耕地的区域。③重金属污染区域具有破碎、复杂和聚集的景观格局，这种景观格局特征与耕地、居住用地和工业用地土壤重金属积累之间的相关性最高。④建设用地斑块的聚集度越高，大多数重金属的积累程度越高。铜、汞、铅和镉的积累程度随着农用地景观多样性和形状复杂性的增加而显著增加。距离采矿点越近，对镉含量增加的影响越明显。
